Additive manufacturing (“AM”) is a technology by which 3-dimensional (“3-D”) geometrically complex parts can be designed on a computer, and data protocols are used to produce the near-net 3-D shaped part directly from a computer-aided design (“CAD”) or computer-aided manufacturing (“CAM”) file. In most common AM processes, material is built up by melting or otherwise building up successive layers of material in different shapes to form a resultant 3-D product. Additive manufacturing, also known as “3-D printing”, is considered distinct from traditional machining techniques, which mostly rely on the removal of material by methods such as machining, filing, turning, milling, grinding, cutting, drilling, etc. In these traditional machining techniques, a base product is formed, and then material is removed therefrom by various known methods to form the resultant 3-D product. Such traditional manufacturing processes that rely on the removal of material are often referred to as “subtractive manufacturing” processes.
Additive manufacturing takes virtual blueprints from CAD/CAM files or animation modeling software and slices them into digital cross-sections for the AM machine to successively use as a guideline for printing. Depending on the AM machine used, material, often with a binding material, is deposited on a build bed or platform in successive layers until the material/binder layering is complete and the final 3-D model has been printed. AM processes are used to make a variety of parts in a range of industries including, but not limited to, jewelry, footwear, industrial design, architecture, engineering and construction (“AEC”), automotive, aerospace, dental and medical industries, education, geographic information systems, civil engineering, and many other fields and industries.
Early AM processes were performed by 3-D printing solid powders in modified inkjet-type printers. While such processes have been comparatively easy for polymers, the 3-D printing of metals has proved to be much more difficult. One prior art technique developed in the 1990s involved the 3-D printing of stainless steel powders mixed with a fugitive organic binder and, at times depending on the particular application, thermoplastic powders. After each printing pass (i.e., deposition of each successive layer of material), a light source cured the polymer to give the additive layer some “green” (i.e., un-sintered) strength. After the 3-D part was built up, it was sintered to make a rigid skeleton of stainless steel, with the fugitive binder and any thermoplastic powder particles melted or burned away. Due to the removal of the fugitive binder and thermoplastic powder, the resulting skeletal stainless steel structure had interconnected porosity. Bronze alloys were identified with good wettability to the stainless steel alloy and were used to finish the 3-D product. The stainless steel skeletal structure could be infiltrated with the bronze alloy by, for example, capillary forces without the need for applied pressure or vacuum assist. While the resulting metal composite product exhibited good strength—approaching, for example, 100 ksi tensile strength—it would typically corrode in moist air and had a high density of about 8.5 g/cm3, depending on the initial porosity of the stainless steel skeletal structure.
AM technology developed rapidly for polymer feedstocks, primarily because melting temperatures for such polymer feedstocks are typically low. The feedstocks could be polymer powders or polymer wire that was melted as the 3-D part was built up. In both cases, the solid feedstock (whether powder or wire) is melted to the liquid state as it is deposited onto the 3-D structure during the AM process, and then cooled to the solid state.
AM technology for metals has been advancing, but the generally high temperatures needed to melt the metals to a liquid state, as well as the oxidation susceptibility of metals, have proven to be difficult obstacles to the widespread application of metal AM techniques. In some known AM techniques, metal powders are fabricated (by atomization, grinding or other means) and are used as feedstocks that are placed into a powder bed. A computer-controlled laser selectively melts regions of the metal powder initially against a metal substrate that serves both as a structural support and a cooling heat sink. After melting a layer of the metal powder onto the metal substrate, the metal powder level is refreshed by spreading or otherwise adding another layer of metal powder on top of that already processed and the technique repeated. This continues until the 3-D part is complete.
However, this technique has several disadvantages including, but not limited to: (1) the laser-sintered parts are essentially welded to the metal substrate and they must be cut off; (2) the build-up of overhanging structure is limited, so support structures for these overhanging structures often have to be built up and machined off; (3) the metal powders are generally expensive and can have consistency issues; (4) the working envelopes are small and expensive in that an AM machine to perform such a process with a one cubic foot envelope currently costs about $600,000; and (5) the metal alloys that are amenable to such techniques are currently limited.
Wire-fed AM processing for metals is a technology pioneered by Sciaky Inc. In such processing, solid wire is fed to a substrate and is then melted to the liquid state by, for example, an electron beam (“EB”). The 3-D structure is built up under CAD/CAM control by what is essentially welding. The working envelop for this technique is generally larger than for other AM techniques. For example, Sciaky Inc. has claimed that 3-D parts as large as 19 feet×4 feet×4 feet can be made using wire-fed AM processing. However, the feature size possible by this technique is quite coarse and the large heat input from the electron beam causes significant residual stresses, which can lead to component distortion. Furthermore, metallurgical defects are undesirably high when using the wire-fed AM technology without adequate process controls.
The commercialization of AM processing for polymer printing is quite mature with many companies available to quote prices to build a limited production run of 3-D printed parts. In fact, polymer AM machines are now available to consumers at relatively low cost as, for example, a child's educational toy, such as the $1200 Cube 3-D Printer by 3D Systems that prints polymer-based parts from a plastic wire feed. However, there is not as much commercial infrastructure for metal AM processes, and there are a limited number of metals and metal alloys that have been successfully 3-D printed up to the present time. In all of the AM work to date, all metal feedstocks are wires or powders, namely solids, that are melted and solidified to form the resultant AM 3-D part. There is thus a need for AM processing techniques that expand the number of metals that can be practically manufactured. Furthermore, AM processing for ceramics is far behind that for metals and polymers.
In a series of patents awarded to Chemical Vapour Deposition Systems, Inc. (also known as CVMR Corporation), Toronto, Canada, methods for production of high-purity nickel and methods for coating nickel onto objects using carbonyl gasses are discussed:                “Nickel Carbonyl Vapour Deposition Apparatus and Method,” U.S. Pat. No. 6,132,518, issued Oct. 17, 2000.        “Nickel Carbonyl Vapour Deposition Process,” Canadian Patent Number 2,206,217, Jan. 7, 2003.        “Nickel Carbonyl Vapour Deposition Apparatus and Process,” Canadian Patent Number 2,307,036, May 27, 2003.        “Closed Loop Carbon Monoxide Self-Contained Nickel Carbonyl Deposition Process,” U.S. Pat. No. 6,048,578, Apr. 11, 2000.        
Claims in these patents identify methods for a continuous process for producing pure nickel or producing pure nickel coatings on objects from impure feedstock. The focus of these claims is the production of elemental nickel. However, no mention is made of producing nickel components of a desired shape and thickness by the use of nickel carbonyl gasses.
The present invention is directed at overcoming one or more of the above-identified problems.